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increafes. To this caufe is to be ascribed, in part, the effect which the dread of spirits in the dark, has on some persons, who are fully convinced in speculation, that their apprehenfions are groundless; and to this also is owing, the effect of any accidental per ception in giving them a momentary relief from their terrors. Hence the remedy which nature points out to us, when we find ourselves overpow. ered by imagination. If every thing around us be filent, we endeavor to create a noise, by speaking aloud, or beating with our feet; that is, we strive to divert the attention from the subjects of our imagination, by presenting an object to our powers of perception. The conclusion which I draw from these observations is, that, as there is no state of the body in which our perceptive powers are so totally unemployed as in fleep, it is natural to think, that the objects which we conceive or imagine, muft then make an impression on the mind, beyond comparison greater, than any thing of which we can have . experience while awake.

From these principles may be derived a simple, and, I think, a satisfactory explanation of what some writers have represented as the most mysterious of all the circumstances connected with dreaming ; the inaccurate estimates we are apt to form of Time, while we are thus employed ;--an inaccuracy which sometimes extends so far, as to give to a single instance, the appearance of hours, or perhaps of days. A sudden noise, for example, suggests a dream connected with that perception ; and, the moment afterwards, this noise has the effect of awaking us ; and yet, during that momentary interval, a long series of circumstances has passed before the imagination. The story quoted by Mr. Addison* from the Turkisha Tales, of the Miracle wrought by a Mahometar


Doctor, to convince an infidel Sultan, is, in such cases, nearly verified.

The facts I allude to at present are generally explained by supposing, that, in our dreams, the rapdi. ity of thought is greater than while we are awake : but there is no necessity for having recourse to such a supposition. The rapidity of thought is, at all times such, that, in the twinkling of an eye, a crowd of ideas may pass before us, to which it would require a long discourse to give utterance ; and transactions may be conceived, which it would require days to realize. But, in sleep, the conceptions of the mind are mistaken for realities; and therefore, our estimates of time will be formed, not according to our experience of the rapidity of thought, but

according to our experience of the time requifite for realizing what we conceive. Something perfectly analogous to this may be remarked in the perceptions we obtain by the sense of fight. When I look into a shew-box, where the deception is imperfect, I see only a set of paltry daubings of a few inches diameter ; but, if the representation be executed with so much skill, as to convey to me the idea of a distant profpect, every object before me swells in its dimensions, in proportion to the extent of space which I conceive it to occupy; and what feemed before to be shut up within the limits of a small wooden frame, is magnified, in my apprehenfion, to an immense landscape of woods, rivers, and mountains.

The phenomena which we have hitherto explained, take place when sleep seems to be complete ; that is, when the mind loses its influence over all those powers whose exercise depends on its will. There are, however, many cafes in which sleep seems to be partial ; that is, when the mind loses its influ. ence over fome powers, and retains it over others. In the case of the somnambuli, it retains its power uver the limbs, but it poflefses no influence over its own

thoughts, and scarcely any over the body; excepting those particular members of it which are employed in walking. In madness, the power of the will over the body remains undiminished, while its influence in regulating the train of thought is in a great meafure suspended ; either in consequence of a particular idea, which engrosses the attention, to the exclufion of every thing else, and which we find it imposfible to banish by our efforts ; or in consequence of our thoughts succeeding each other with such rapidity, that we are unable to stop the train. In both of these kinds of madness, it is worthy of remark, that the conceptions or imaginations of the mind becoming independent of our will, they are apt to be mistaken for actual perceptions, and to affect us in the same manner.

By means of this supposition of a partial sleep, any apparent exceptions which the history of dreams may afford to the general principles already stated, admit of an easy explanation.

Upon reviewing the foregoing observations, it does not occur to me, that I have in any inftance transgressed those rules of philofophising, which, fince the time of Newton, are commonly appealed to, as the tests of found investigation. For, in the first place, I have not supposed any causes which are not known to exist ; and secondly, I have shewn, that the phenomena under our consideration are necessary consequences of the causes to which I have referred them. I have not supposed, that the mind acquires in fleep, any new faculty of which we are not conscious while awake ; but only (what we know to be a fact) that it retains some of its powers, while the exercise of others is suspended : and I have deduced lynthetically, the known phenomena of dreaming, from the operation of a particular class of our faculties, unconnected by the operation of another. I flatter myself, therefore, that this inquiry will not


only throw some light on the state of the mind in sleep; but that it will have a tendency to illustrate the mutual adaptation and subserviency which exifts among the different parts of our constitution, when we are in a complete pofseffion of all the faculties and principles which belong to our nature.*



Of the Influence of Affociation on the Intellectual

and on the Active Powers.


Of the Influence of casual Asociations on our speculative


THE Affociation of Ideas has a tendency to warp our speculative opinions chiefly in the three following ways:

Firit, by blending together in our apprehenfions, things which are really distinct in their nature ; se as to introduce perplexity and error into every process of reasoning in which they are involved.

Secondly, by mifleading us in those anticipations of the future from the pait, which our conftitution disposes us to form, and which are the great foundation of our conduct in life.

Thirdly, by connecting in the inind erroneous

* See Note [O.]

opinions, with truths which irresistibly command our affent, and which we feel to be of importance to human happiness.

A hort illustration of these remarks, will throw light on the origin of various prejudices ; and may, perhaps, suggest fome practical hints with respect to the conduct of the understanding.

I. I formerly had occafion to mention several instances of very intimate associations formed between two ideas which have no necessary connection with each other. One of the most remarkable is, that which exists in every person's mind between the notions of colour and of extension. The former of these words expresses (at least in the sense in which we commonly employ it) a sensation in the mind; the latter denotes a quality of an external object ; so that there is, in fact, no more connection between the two notions than between those of pain and of folidity ; * and yet, in consequence of our always perceiving extension, at the same time at which the senfation of colour is excited in the mind, we find it impossible to think of that sensation, without conceiving extension along with it.

Another intimate allociation is formed in every mind between the ideas of space and of time. When we think of an interval of duration, we always conceive it as something analogous to a line, and we apply the same language to both subjects. We speak of a long and short time, as well of a long and short dift-. ånce, and we are not conscious of any metaphor in doing so. Nay, so very perfect does the analogy appear to us, that Boscovich mentions it as a curious circumstance, that extension should have three dimensions, and duration only one.

This apprehended analogy seems be founded wholly on an association between the ideas of space

* See Note [P.]

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